Bioprosthetic heart valves can replace defective native or previous prosthetic valves in patients. Bioprosthetic heart valves generally include a plurality of leaflets attached or otherwise coupled to a frame, stent, or other support structure. The leaflets may be formed from a synthetic material or biological tissue, such as bovine pericardium.
Sutures may be used to secure the leaflets to the support structure of the valve. Typically, a person, such as physician or even a specially trained seamstress, uses a needle and suture thread to pass one or more sutures through the leaflet and the support structure. This process is generally a manual operation and, consequently, may introduce a degree of variation between different sutures placed on a single valve. For example, the placement or even tightness of the individual sutures on a prosthetic valve may vary to some extent even with the most skilled artisan. The variation in which the sutures are placed in the valve may adversely impact the hemodynamic performance of the leaflets after they are secured to the support structure. For example, the particular location of a suture may impact the stress and/or strain characteristics of the leaflet.
In addition, in a multiple leaflet prosthetic valve, one or more leaflets may have different performance characteristics from the remaining leaflets because one or more sutures are inserted slightly off from their desired locations. Variability is thus introduced within a single valve (e.g. intra-valve variability), which may adversely impact the valve's hemodynamic performance. Similarly, even if there is no variability between individual leaflets on a single valve, variability may be introduced between different valves (e.g., inter-valve variability). This latter problem may arise, for example, because a number of different persons are employed to affix the individual leaflets to support structures or otherwise assemble the valves.
U.S. Pat. No. 5,662,705 discloses a method of manufacturing and testing a tissue heart valve during open heart surgery. A piece of autologous tissue from the body of the patient is cut with a plurality of holes being formed in the tissue by a cutting die. The tissue is situated between first and second stents so that the holes are registered with corresponding tissue alignment members in one of the stents, and the stents are positioned together to securely clamp the tissue therebetween.
In some prosthetic heart valve designs, the suture holes may be located close to the edge of the leaflets. When such leaflets are formed from bovine pericardium or other biological tissue, a die cutter may have difficulty punching or otherwise forming holes near or adjacent to the edge of the leaflets.
Thus, apparatus and methods for making leaflets and/or prosthetic valves that reduce intra-valve and/or inter-valve variability may be useful.